Image sensors are semiconductor devices which may convert an optical image into an electrical signal. Examples of types of image sensors are charge coupled device (CCD) image sensor and a complementary metal oxide semiconductor (CMOS) image sensor (CIS). A CIS image sensor may include a photodiode and a metal oxide semiconductor (MOS) transistor in each unit pixel. A CIS image sensor may sequentially detects electrical signals of respective unit pixels in a switching mode to realize an image. A CIS image sensor may include a photodiode region that receives an optical signal and converts the optical signal into an electrical signal. A CIS image sensor may include a transistor region that processes the electrical signal. A CIS image sensor may have a metal line connecting a floating region of a unit pixel with a drive transistor of the unit pixel. However, the metal line may cross a photodiode region of the unit pixel, which may decrease an aspect ratio of the image sensor. A decrease in the aspect ratio may be a limitation in downscaling of image sensor chip size, thus creating complications in design and manufacturing.